Synthesis of Novel 6-Aryloxy-4-chloro-2-phenylpyrimidines as Fungicides and Herbicide Safeners

Fenclorim is a commercial herbicide safener with fungicidal activity used for chloroacetanilide herbicides, which might be suitable as a lead compound for screening novel fungicides. However, little has been reported so far on the structure-activity relationship of fungicidal activities of fenclorim or its analogues. Here, a series of 4-chloro-6-substituted phenoxy-2-phenylpyrimidine derivatives was synthesized by a substructure splicing route using fenclorim as a lead compound. The structures of synthesized derivatives were characterized by H-1 NMR, C-13 NMR, and HRMS. Their fungicidal and herbicide safening activities were then evaluated. The results revealed that compound 11 had the best fungicidal activity against Sclerotinia sclerotiorum and Thanatephorus cucumeris, which was better than that of the control pyrimethanil. Moreover, compounds 3, 5, and 25 exhibited excellent safening activities against fresh weight, plant height, and root length, respectively. Such activities were significantly improved when compared to fenclorim. In summary, these findings look promising for the preparation of new fungicides and herbicide safeners based on the structure of fenclorim.